# Relationship history for MSHA mine 2301973

Current hierarchy: **Case Ralph → Ralph Case Mining & Excavating → Portable Operation #1**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **operator_operates_mine:** Ralph Case Mining & Excavating → Portable Operation #1; 1987-09-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Case Ralph → Portable Operation #1; 1987-09-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Case Ralph → Ralph Case Mining & Excavating; 1987-09-01 to current/open; source msha-controller-operator-history